Mowing machine

ABSTRACT

A mowing machine has a main frame made up of driving units and intermediate pieces which are mounted alternatively on a tie member. The tie member is normally under tension to compress the driving units and the intermediate pieces together to make the main frame substantially rigid. The tie member is positioned substantially centrally of the driving units and the intermediate pieces so as to provide even loading of their mating faces. The driving units preferably have cutting units with flexible hoods. The cutting units are driven by a common continuous drive shaft through bevel gearing and the direction of rotation of each cutting unit can be changed by removing the gear and replacing it the other way round within the driving unit housing on the driving shaft.

RELATED APPLICATIONS

This is a division of application Ser. No. 416,047 filed Sept. 7, 1982,U.S. Pat. No. 4,476,666 of Oct. 16, 1984.

SUMMARY OF THE INVENTION

This invention relates to a mowing machine having a main framecomprising a plurality of driving units on which cutting units aremounted for rotation about upwardly directed axes. A tie member extendsthrough the driving units.

Such mowing machine are disclosed in Dutch patent application Nos.76.05371 and 79.07139. This construction has the advantage of a simpleassembly of the main frame and of the possibility of lengthening orshortening the main frame, and thus of the machine as a whole, in asimple manner. A disadvantage of the known machines, however, is thatthe driving units are not uniformly loaded.

According to the present invention, the tie member is located at aconsiderable distance both from the leading and trailing edges of themain frame in a manner such that a tensile force exerted on the tiemember is applied at least substantially centrally to the driving units.

In a further embodiment of the machine according to the invention a hoodis arranged near at least part of the path covered by the cutters.

In devices known from the French patent specifications Nos. 1,483,721,1,499,211 and 1,524,150 and from Swiss patent specification No. 68,124the hood serves as a protecting member for subjacent construction partsand--if the hood rotates with the cutting units--as a transport devicefor the crop cut by the mowing cutter.

Such known mowing machines involve the drawback that stones lying in thecrop to be mown are carried to the rear by the mowing cutters and can bejammed between the top side of a frame beam located below the mowingcutters and comprising the driving gear of the mowing unit and theunderside of the hood or between the ground and the hood when thedriving gear is disposed above the same. Jamming of stones or otherobjects may have serious consequence for the construction of the mowingmachine, since material destruction may occur. One object of theinvention is to avoid this disadvantage insofar as possible.

According to the invention the hood is flexible.

Owing to the flexible structure of the hood fastened to the machine itcan yield to objects jammed on the bottom or top side so that theseobjects can as yet be conducted away.

For a better understanding of the present invention and to show how itmay be carried into effect, reference will now be made, by way ofexample, to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a mowing machine hitched to a tractor;

FIG. 2 is a plan view of part of the mowing machine of FIG. 1 on anenlarged scale;

FIG. 3 is a plan view of a further part of the mowing machine of FIG. 1on an enlarged scale;

FIG. 4 is a partly sectional view taken in the direction of the arrow IVin FIG. 2;

FIG. 5 is a sectional view taken on the line V--V in FIG. 2;

FIG. 6 is a sectional view taken on the line VI--VI in FIG. 2;

FIG. 7 is a sectional view taken on the lines VII--VII in FIG. 2;

FIG. 8 is a sectional view taken on the line VIII--VIII in FIG. 2;

FIG. 9 is a schematic plan view of the mowing machine of FIGS. 1 to 8;

FIG. 10 is a plan view of two cutting units driven in opposite senses inthe machine shown in FIG. 1;

FIG. 11 is a horizontal rear view of the part of the machine shown inFIG. 10, taken in the direction of arrow XI in FIG. 10 the cutting unitsbeing shown partly in an elevational view and partly in a sectionalview;

FIG. 12 is a plan view of a cutting unit of a further embodiment;

FIG. 13 is a rear view of one of the cutting units shown in FIG. 12partly in an elevational view and partly in a sectional view;

FIG. 14 is a sectional view taken on the line XIV--XIV in FIG. 12.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The mowing machine shown in FIG. 1 comprises a fastening trestle 3 whichis hitched to a three-point lifting device 1 of a tractor 2. At therear, the trestle 3 carries an intermediate frame 4, which is pivotablewith respect to the trestle 3 about a substantially horizontal pivotalaxis 5 extending in the intended direction of operative travel of themachine, as indicated by an arrow A in FIGS. 1, 2 and 9. In theillustrated embodiment, the axis 5 lies substantially in the vertical,longitudinal central plane of the tractor 2. The intermediate frame 4extends away from the axis 5 transversely of the direction A to aposition substantially level with a lateral boundary face of the tractor2.

A main frame 6 is connected to the end of the intermediate frame 4 awayfrom the pivotal axis 5 and is pivotable with respect to theintermediate frame 4 about a pivotal axis 7. The axis 7 is parallel tothe axis 5 and is located just within the lateral boundary of thetractor 2. Viewed from above, the main frame 6 is in line with theintermediate frame 4 and thus also extends transversely of the directionA.

In the illustrated embodiment the main frame 6 carries six cutting units8, which are drivable in rotation about upwardly directed rotary axes 9.The rotary axes 9 may be vertical, but preferably they are tiltedslightly forward, with respect to the direction A, from bottom to top.Each cutting unit 8 is provided with one or more outwardly extendingcutters 10. The tip of a cutter 10 of the cutting unit nearest theintermediate frame 4 describes a circle which extends substantially upto the nearest boundary face of the tractor 2, that boundary face beingparallel to the direction A.

The intermediate frame 4 and the main frame 6 are pivotable with respectto the trestle 3 about an upwardly directed pivotal axis 11 which liessubstantially in the vertical longitudinal central plane of the tractor2 and which provides the connection between the intermediate frame 4 andthe trestle 3. In normal operation, pivoting about the axis 11 isprevented by an overload mechanism 12 which is arranged at a distancefrom the central longitudinal plane of the tractor and connects theintermediate frame 4 to the trestle 3.

A framework 13 extends over the main frame 6. Flexible walls aresuspended from the periphery of the framework 13 and extend to theground to protect bystanders against objects such as stones which mightbe thrown up by the cutting units 8.

The mowing machine has an input shaft which is journalled in a sleeve 15and which can be connected to the power take-off shaft of the tractor 2by an auxiliary shaft 14. The sleeve 15 is rigidly secured to theintermediate frame 4 and extends substantially horizontally in thedirection A. The axis of the input shaft 16 coincides with the pivotalaxis 5. The input shaft 16 projects from the rear end of the sleeve 15and the projecting portion carries a pulley 17. Near the end of theintermediate frame 4 adjacent the main frame 6 there is a pulley 18which is mounted on a shaft 19 journalled in lugs 20 and 21 provided onthe intermediate frame 4 and in a gear box 22. The gear box 22 ispivotable with respect to the lugs 20 and 21 and is rigidly secured tothe main frame 6. The axis of the shaft 19 coincides with the pivotalaxis 7. The pulley 17 is drivably connected to the pulley 18 by means ofone or move V belts 23 running around the two pulleys. The diameter ofthe pulley 17 is larger (for example three times larger) than thediameter of the pulley 18. The shaft 19 carrying the pulley 18 isprovided with a bevel gear wheel 24 (FIG. 4), which meshes with a bevelgear wheel 25, the rotary axis of which is substantially horizontalduring operation and intersects the pivotal axis 7 at right angles. Thegear wheel 25 is journalled in a substantially vertical gear box 26,which is rigidly secured to the gear box 22. The shaft of the bevel gearwheel 25 is provided with a gear wheel 27 which is located inside thegear box 26 and meshes with an intermediate gear wheel 28 disposed belowit. The intermediate gear wheel 28 meshes with a gear wheel 29 disposedbeneath it. The rotary axes of the gear wheels 27, 28 and 29, which areall spur gears, are parallel to one another and located vertically oneabove the other. The diameter of the bevel gear wheel 24 issignificantly larger than the diameter of the bevel gear wheel 25, andthe substantially equal diameters of the gear wheels 27 and 28 areconsiderably larger than the diameter of the lower gear wheel 29. Thegear box 26 has at the bottom an outwardly projecting collar 30 (FIG.4), which surrounds the shaft of the gear wheel 29 extending in the samedirection. The outwardly directed end part of the shaft of the gearwheel 29 is provided with axial splines co-operating with further axialsplines on the inside of a sleeve 31 which fits over the protrudingshaft portion of the gear wheel 29 and is located inside the collar 30.The end of the sleeve 31 facing the gear wheel 29 abuts a bearing 32Awhich is located between the sleeve 31 and the gear wheel 29 and is oneof the bearings supporting the gear wheel 29. The end of the sleeve 31away from the bearing 32A projects beyond the outer end of the shaftbearing the gear wheel 29. The sleeve 31 is surrounding by part of a tiepiece 32 having a bore, opening towards the gear wheel 29, which gripsthe sleeve 31. This part of the tie piece 32 is rotationally connectedwith the sleeve 31 in a manner not shown, for example, by means ofsplines. The part of the tie piece 32 away from the gear wheel 29 isalso shaped as a sleeve, but with a smaller diametral dimension. Thispart defines an outwardly opening recess having a square transversecross-section. This square recess opens into the bore at a shoulder 33.Before slipping the tie piece 32 onto the sleeve 31, a supporting plate34 is disposed on the shoulder 33, so that this plate 34 is clampedbetween the sleeve 31 and the shoulder 33.

The main frame 6 is clamped to the collar 30 in a manner to be describedmore fully later, and extends outwardly away from the collar.

Before describing in detail the construction and assembly of the mainframe, the associated driving units and the cutting units, the generalstructure of the main frame will be discussed. The main frame 6 is madeup of a sequence of separate parts comprising (beginning at the collar30) a separate intermediate piece 35 (FIG. 4), a separate driving unit36 (comprising a rotatable part at the top forming the cutting unit 8),an intermediate piece 35, another driving unit 36 (again comprising arotatable cutting unit 8), an intermediate piece 35 and so on. Theoutermost part in this sequence is a driving unit terminated by an endpiece to be described more fully later. The intermediate pieces 35 areseparate parts which may have identical shapes and dimensions. As viewedin the direction B (FIG. 4) or in the opposite direction, the end facesof the intermediate pieces 35 all have the same shape and dimensions.The lengths of the intermediate pieces 35 measured in the direction Bmay be the same for all of the intermediate pieces, but they canalternatively be wholly or partly different. Basically the driving units36 are identical. This also applies to the cutting units 8 provided onthe driving units 36, but the lengths of the cutters 10 may be differentfor different cutting elements.

For the sake of clarity, FIG. 8 is an elevational view, in the directionopposite the direction B. The solid-line part of FIG. 8 applies to allof the intermediate pieces 35. The solid-line part of FIG. 8 togetherwith the broken-line part applies to an elevational view of a drivingunit 36 taken as indicated above opposite the direction B. Theintermediate pieces 35 and the housings of the driving units 36 are madefrom, for example, cast iron. FIG. 8 shows that the lateral boundaryfaces of the intermediate pieces 35 and of the driving units 36 havethree holes 37, 38 and 39. These holes extend in the direction B acrossthe part concerned up to the other boundary face. The hole 37 serves toreceive a single main shaft 41 extending in the direction B through allof the intermediate pieces 35 and driving units 36. The hole 38 servesto receive a tie member in the form of a tie rod 42 which also extendsthrough all of the intermediate pieces 35 and driving units 36. This tierod is heavily loaded in tension and is anchored at its ends on theinner and outer driving unit or intermediate piece respectively in thecollar 30 so that all driving units and intermediate pieces aresubjected to a compressive force parallel to the direction B which isequal to the tensile force in this tie rod.

The hole 38 for receiving the tie rod is located approximately at themiddle of the dimension of the end face in the direction A so that thecompressive force exerted by the tie rod on the intermediate pieces anddriving units acts centrally in order to avoid gaps between theintermediate pieces and the driving units and in order to obtain anassembly which is resistant to bending, while the entire mating surfaceof each intermediate piece and driving unit is uniformly loaded.

On the side of the hole 38 away from the hole 37 the end face of eachintermediate piece and driving unit has a hole 39. This hole 39 isimportant in the manufacture of the castings for releasing the cores ofthe castings. The wall thickness of each intermediate piece and drivingunit is relatively small so that a large hollow space can be enclosedand the weight can be kept low, while the structural rigidity issufficient. The general form of the intermediate pieces and the housingsof the driving units, as viewed in the direction A, is shown in FIG. 4.In the central region of each intermediate piece 35 the vertical andtransverse dimensions are smaller than in the short regions near theadjacent driving units. In particular, it is significant that thecentral region of the leading edge of the intermediate piece 35 is setback from the end regions of the leading edge. The plan view of FIG. 2indicates the distance 40 measured in the direction A between theleading edge of an intermediate piece 35 (viewed on plan) and theforemost boundary of the main driving shaft 41 of the main frame. Inorder to maximize the amount by which the central region of the leadingedge of the intermediate piece is set back from the end regions, thedimension 40 is minimized and is substantially equal to the wallthickness of the casting of the intermediate piece. Consequently, theleading edge is close to the opening for the main driving shaft. Thus,when the cutters of neighboring driving units are rotating in oppositesenses, (as shown by way of example in FIG. 2) sticking of crop cuttingswhich form in practice into a growing crust on the leading edge of aframe part in the region where the cutters of two adjacent driving unitsmove backwards) can occur without being able to increase forwardly to apoint where the circles described by the outermost tips of the cuttersintersect, where the crust would adversely affect the mowing operation.The dimension between the leading edge of the intermediate piece and thepoint of intersection of the mowing circles is too large to be coveredby the sticking crop cuttings, since the front portion of the crust isconstantly breaking off to an extent such that bridging the gap betweenthe leading edge of the intermediate piece and the point of intersectionof the mowing circles cannot occur.

The tie rod 42 is shown in FIGS. 2 and 5. The tie rod 42 extends throughall of the intermediate pieces and driving units and comprises aseamless, drawn, thickwalled tube. Alternatively a differently shapedtube or solid rod may be used. At the inner end of the main frame 6 thetie rod 42 is provided with a welded head 43 (FIG. 2) bearing on thesurfaces of the gear box 26 directed towards the intermediate frame 4.As shown in FIG. 4, the tie rod 42 is thus located behind the axis ofthe gear wheel 29, with respect to the direction A. The two upwardlydirected walls of the gear box 26 have holes through which the tie rod42 passes. From FIG. 3 it will be appreciated that the outermost end ofthe tie rod 42 has an internal screwthread receiving a bolt 44. The headof the bolt bears on the outer surface of an end piece 45 in the form ofa plate which is in contact with the outer end face of the outermostdriving unit 36. The length of the tie rod 42 is such that a small spaceis left between its outer end and the inner surface of the end piece 45.By tightening the bolt 44 to a maximum torque of, for example,twenty-four kilograms per meters, the tie rod 42 is placed under tensionso that it exerts, through the end piece 45, a compressive force on theintermediate pieces and driving units. The end piece 45 extendsrearwardly and slopes inwardly (FIG. 3) to provide a support for a swathboard for defining the outer edge of the mown swath of crop depositedbehind the machine in operation. Under the action of the compressiveforce applied by the tie rod 42, the intermediate element 35 locatednearest to the gear box 26 bears, through an intermediate ring, on thecollar 30, which has an outer face that matches the contacting face ofthe intermediate ring.

FIG. 6 shows one of the driving units 36 clamped between twointermediate pieces 35 (see the side elevation of FIG. 8 as a whole).The main drive shaft 41 passing through all of the intermediate pieces35 and driving units 36 is a solid shaft of non-circular cross-section.In the illustrated embodiment the shaft 41 has a square cross-section,but it could alternatively be rectangular, hexagonal or circular with aflat side or a key way. The sides of the square cross-section are twelvemillimeters long. In each driving unit 36 the shaft 41 passes through amatching square hole in a bevel gear wheel 46, which meshes with a bevelgear wheel 47, the axes of these bevel gear wheels intersecting eachother at right angles. The gear wheel 46 has sixteen teeth and the gearwheel 47 has thirty three teeth. A shaft 48 extends upwardly from thegear wheel 47 and has a cylindrical part 49 which is in close contactwith the cylindrical inner boundary of a hub 50 of the associatedcutting unit 8. The interface between the cylindrical portion 49 and theinner wall of the hub 50 thus constitutes a centering face for theposition of the hub 50.

A locking ring 51 is bolted to the casting forming the housing of thedriving unit 36. The locking ring 51 is also a casting and has anL-shaped radiall cross-section. The inner surface of the locking ring 51is smoothly reamed and receives two bearings 52 and 53 disposed oneabove the other. The inner races of the bearings 52 and 53 support theouter surface of the lower part of the hub 50. The top part of the hub50 has a flange extending over the upper bearing 52. The top surface ofthe flange serves as a supporting surface for an annular cutter holder54, which slopes downwardly on all sides away from the outer peripheryof the top part of the hub 50 and then extends as a flat ring at rightangles to the centerline of the shaft 48. The flat ring carries, in thisembodiment, two mowing cutters 10 disposed diametrically opposite eachother. Each of the cutters 10 is fastened to the cutter holder 54 in apivotable manner by means of a bolt which is parallel to the centerlineof the shaft 48. The inner periphery of the upper and inner part of thecutter holder 54 defines a square hole which is a close fit over araised part 55 of square shape, as viewed on plan, on the top surface ofthe hub 50.

The shaft 48 comprises a splined portion located inside the hub 50 andabove the cylindrical part 49. The splines cooperate with furthersplines in the inner periphery of the hub 50. Above the splined portionthe shaft 48 has a screwthreaded portion 56. A cap 57 is fitted over thescrewthreaded portion 56 to secure the central part of the cutter holder54. The cap 57 has a recess on the underside which receives the squareraised part 55 of the hub 50. A nut 58 is screwed onto the screwthreadedportion 56 to clamp the cap 57 to the cutter holder 24 and to the topsurface of the hub 50.

The inner race of the lower bearing 53 bears on a shoulder 59 of theshaft 48, this shoulder constituting a centering surface which islocated directly above the gear wheel 47 so that the lower bearing 53extends deeply into the housing of the driving unit 36 and the totalheight of the cutting unit can be limited, which is conducive tostability in operation. The gear wheel 46 is journalled in a bearing 60,the outer race of which is supported in the hole 37 of the castingforming the housing of the driving unit 36. On the side of the bearing60 facing the adjacent intermediate piece 35 there is a locating ring 61which is arranged in the hole 37 and projects from the end face of thecasting. Between the bearing 60 and the locating ring 61 there is aSeeger ring (circlip) 62 located in a groove in the wall of the hole 37.A seal 63, for example, formed by an O-ring, is arranged between theouter race of the bearing 60 and the boundary of the hole 37. As viewedin FIG. 6 a bearing 60, an O-ring 63, a Seeger ring (circlip) 62 and alocating ring 61 are provided in a similar arrangement on the other sideof the driving unit 36.

The gear wheel 46 is integral with a sleeve 64 extending towards thebearing 60 farther from the gear wheel 46, which bearing is axiallysupported on a shoulder provided at the end of the sleeve 64. The Seegerrings (circlips) 62 prevents the bearing 60 from moving outwardly of thedriving unit 36.

The space around the gear wheels 46 and 47 are filled with lubricantsuch as grease. The presence of the sleeve 64 results in thegrease-filled part of the driving unit 36 being held within a closedspace so that the grease cannot penetrate to the interior of the sleeve64. Consequently, if the main drive shaft 41 is removed and the drivingunit 36 is used as a separate unit, the grease cannot leave the drivingunit.

In FIG. 6, the gear wheel 46 is shown on the left-hand side of the axis9 of the shaft 48. The locating ring 61 is a sliding fit allowingmovement of the ring in the unit 36 so that, when the driving unit 36 isused as a separate unit, the ring can be readily removed. After theremoval of the Seeger ring (circlip) 62 the bearing 60 can also beremoved, since the bearing 60 is held in place by the Seeger ring(circlip) and the sleeve 64 rather than by the fit of the bearing 60 inthe housing of the driving unit. These conditions also apply to thecentering ring 61, the Seeger ring (circlip) 62 and the bearing 60 onthe right-hand side in FIG. 6. This means that the gear wheel 46 and thesleeve 64 can be removed and replaced the other way round, the gearwheel 46 then being on the right-hand side, as viewed in FIG. 6 so thatit engages the opposite side of the gear wheel 47. When the main driveshaft 41 is driven in the same direction as before, the cutting unit 8is driven in the opposite direction of rotation.

Since the lubricant contained in the driving unit 36 is confined in aclosed space, it is necessary to provide vent means shown in FIG. 7. Aholder 65 is screwed into a tapped hole in the locking ring 51. Theholder 65 has a bore communicating with the space around the gear wheels46 and 47. The bore contains a compression spring 66. On the undersidethe compression spring 66 bears on the top side of a flap or plunger 67,the underside of which bears on a shoulder in the continuous bore in theholder 65. At the top the holder 65 has a discontinuous collar 68 belowwhich there is a second discontinuous collar 69, which bears on thelocking ring 51 in the mounted state. The top end of the spring 66 is incontact with the underside of a cap 70 of readily deformable materialsuch as brass which is fitted over the upper collar 68 and crimped, bymeans of pincers, in the region between the two collars 68 and 69. Thecap 70 is crimped only on two opposite sides, and consequently betweenthe crimped parts the cap is slightly deformed outwardly so that anaperture is formed extending from the bore of the holder 65 along thediscontinuous collar 68 to the region between the two collars and thenceto the open air. The spring 66 normally holds plunger 67 closed, butwhen heat is developed inside the driving unit 36 the lubricant, whichthen tends to expand, can lift the flap 67 and escape through anaperture 67A to the bore of the holder 65 and along the path describedabove. The escaping lubricant is in general formed by a mixture of airand grease particles. After the cutter holder 54 is removed, the holder65 can be unscrewed and, if necessary, the driving unit may bereplenished with grease through the opening thus formed.

From FIGS. 2 and 8 it will be appreciated that, viewed in the directionof movement A, the leading edges of the tops of the driving units arelocated in front of the leading edges of the adjacent intermediatepieces 35. This is a consequence of the shaft 48 of the cutting unit 8of each of the driving units being placed as far forward as possiblewith respect to the neighboring intermediate pieces in order to obtain,in the opposite direction of rotation of the cutting units 8, an overlapof the cutters located as far as possible in front of the leading edgeof the adjacent intermediate piece 35. An additional consideration, asreferred to above, is the effect of a growth of a layer of crop cuttingssettling on the leading edge of the intermediate piece. In FIG. 2 theleading edges of the top parts of the housings of the driving units 36protruding in front of the leading edges of the intermediate pieces aredesignated by reference numeral 71. Viewed on plan in FIG. 2 the leadingedge of each driving unit is arcuate and subtends an angle of about 150°or more in front of the leading edge of the adjacent intermediate piece.From the leading edge 71, the front wall of each driving unit isinclined downwardly from the front to rear and adjoins on the undersidethe underside of the driving unit (FIG. 8).

Each driving unit 36 comprises a releasable shoe 72, the shape of which,in side view, generally follows the form of the front, underneath andrear surfaces of the housing of the driving unit (FIG. 5). The shoe 72fits around the leading edge 71 of the driving unit and then slopesdownwards and rearwards; subsequently it extends over the bottom face ofthe housing and curves upwardly behind the rear wall of the housing.This shoe 72 is fastened to the housing only at the rear by two bolts73. The shoe 72 not only provides a sliding and wear-resistant surfacefor the driving unit (the bottom face of each adjacent intermediatepiece 35 is located above the ground as can be seen, for example, fromFIGS. 4 and 6), but also enables a protecting plate 74 (FIG. 5), to berigidly secured to the front of the shoe 72. The protective plate 74 isfastened at a distance of about two to three centimeters, preferablyabout 2.5 centimeters, below the outer edge of the cutter holder 54 andextends parallel to the outer edge of the cutter holder 54. The width ofthe protective plate 74, measured in the direction B (FIG. 4), issubstantially equal to that of the driving unit and, viewed on plan, theouter boundary of the plate 74 approximately corresponds with that ofthe outer edge of the cutter holder 54. The plate 74 protects thecutting unit 8 from stones and other objects which might otherwisepenetrate below the cutters 10 to the driving unit and damage thecutting unit 8 by an upward movement.

The main drive shaft 41 of the mower is made from a single length ofmaterial and extends from the collar 30 of the gear box 26 to the outerside of the outermost driving unit. This shaft is comparatively verythin and this thinness of the shaft appreciably contributes to the lowvalue of the dimension 40 in FIG. 2. The polar moment of resistance ofthe main driving shaft 41 amount to about 0.36 cm³ and transfers innormal operation a power of about thirty horsepower (twenty-twokilowatts) (22 L kW) with a torsional moment of about 230 kilograms percentimeters (2220 Ncm). This comparatively low torsional moment and theconsequent small diameter of the main drive shaft 41 can be attained bydriving the shaft 41 at a comparatively high speed of revolution. At aspeed of the power take-off shaft of the tractor of 540 r.p.m. the shaft19 is driven in the illustrated embodiment, at a speed of 1370 r.p.m.owing to the ratio between the diameters of the pulleys 17 and 18. Thetransmission ratio between the gear wheels 24 and 25 (23 and 15 teethrespectively) and the transmission ratio between the gear wheels 27, 28and 29 (seventy-seven, seventy-seven and seventeen teeth respectively)provide a speed of the drive shaft 41 of about 9500 r.p.m. Owing to thetransmission ratio between the gear wheels 46 and 47 (sixteen andthirty-three teeth respectively), the speed of each shaft 48 (and henceof each cutting unit 8) will be about 4600 r.p.m. The speed ofrevolution of the input shaft 16 of the machine is thus first convertedinto the high value of the speed of the shaft 41 and then reduced.Depending on the diameter of the circle described by the tips of thecutters 10 (for example, about thirty centimeters for adjacent cuttingunits 8 rotating in the same direction and 35 or more for adjacentcutting units rotating in opposite directions) the tips of the cuttersmove at about seventy to eighty-five meters per second.

An important advantage of the comparatively thin main drive shaft 41 isthat, during operation, this shaft can withstand an appreciabletorsional deformation. With an overall length of the shaft 41 of onehundred, sixty-five centimeters the angular displacement between theends of the shaft is slightly more than 9° in normal operation. Thetotal permissible angular displacement between the ends of the shaft isabout 46° before the yield point of the material is reached. Theelasticity of the shaft 41 enables external forces exerted on thecutting units by impact with obstacles such as stones and the like to beabsorbed without resulting in damage to the machine. The safety factorup to the yield point of the shaft 41 is approximately five. Also in thecase of a jolting start and running down of the rotating cutting unitsthe elasticity of the shaft 41 is important.

As shown in FIG. 6, each gear wheel 46 has a cylindrical cavity 75 whichopens to the outside on the side facing the outer side of the drivingunit. The cylindrical wall of the cavity 75 has a continuous groove 76.The cavity 75 and the groove 76 are only used in the outermost drivingunit 46 as is shown in FIG. 3. In this outermost driving unit the gearwheel 46 is arranged on that side of the driving unit which is farthestfrom the gear box 26, since the cutters 10 driven by this driving unithave to move inwardly at the front of the machine. The cavity 75 is,therefore, open to the outside. The continuous groove 76 can receive aSeeger ring (circlip) which provides a stop in outward direction for theadjacent end of the main drive shaft 41. The inner end of the shaft 41is located by abutment with the supporting plate 34 mentioned above withreference to FIG. 4. In this way the shaft 41 is prevented from movingaxially (except for a small clearance) and it is retained axially bystops which rotate with the shaft so that they do not give rise to wear.

The cutting unit 8 arranged on the outermost driving unit 36 (that is tosay at the free end of the main frame 6) is preferably provided with adifferently shaped cutter holder 54 and hub 50, the cutter holder 54measured in a vertical direction being appreciably higher than thecutter holders shown in FIGS. 4 and 6, that is to say, preferably two tofour times higher than the cutter holders shown. The general design maybe the same, i.e. an upwardly converging truncated cone. The reason forthis is that the outermost cutter holder 54, the front side of whichmoves inwardly, contributes to the establishment of the lateral edge ofthe mown swath. The hub 50 is also higher, while the same cap 57 can beused as in the other cutter holders.

When viewed in a horizontal direction and in the direction A (FIGS. 4and 6), the top face of each intermediate piece 35 is located at adistance (1.5 to 2.5 centimeters) below the bottom face of the lockingring 51 of the adjacent driving units 36 in order to minimize anyhindrance of the passage of mown crop to the rear over and across theintermediate pieces. The distance between the top side of the part ofthe main drive shaft 41 in each intermediate piece 35 and the top faceof the intermediate piece itself is mainly occupied by the wallthickness of the intermediate piece 35. This is another advantage of thesmall diameter of the main drive shaft 41 allowed by the comparativelyhigh speed of rotation of this shaft.

As stated above the cutters 10 (two of which are shown on each cuttingunit 8) are arranged on the outer, lower rim of the cutter holder 54 soas to be freely pivotable at their inner ends about a pivotal axisparallel to the axis 9. The cutters 10 have a twisted form so that, withrespect to the direction of rotation, the leading edge of each cutter isat a lower level than the trailing edge.

The mowing machine described may be assembled in various ways inaccordance with the user's needs. The intermediate pieces 35 and thedriving units 36 (on which the cutting units are or will be mounted) arealternately mounted on the tie rod 42, for example, first anintermediate piece 35, using the associated holes 8 (through whichpasses the tie rod 42), then a driving unit 36 (also using the holes38), then another intermediate piece 35, and so on until the desirednumber of driving units and cutting units 8 is attained. The tubular tierod 42 is preferably a close fit in the holes 38 (FIGS. 5 and 8), butthis is not essential. In assembling the intermediate pieces and drivingunits the location of these components relative to each other is ensuredby the locating rings 61 (FIG. 6) each abutting the Seeger ring(circlip) 62 of the adjacent driving unit and abutting a shoulder in theadjacent intermediate piece. Such a shoulder is also provided in thecollar 30 of the gear box 26 (FIG. 4). By means of these locating rings61 the relative positions of the intermediate pieces and the drivingunits as well as of the first intermediate piece and the collar 30 areaccurately established. Since the contacting faces of the intermediatepieces and the driving units are smooth, relative rotation of thesecomponents might occur, but this is prevented by the presence of thedraw rod 42 at a distance behind the locating rings 61 and by the highcompressive force exerted by the tie rod 42 on the intermediate piecesand the driving units, this force being satisfactorily absorbed by thecast-iron housings of the intermediate pieces and driving units, it isadvisable to pass the main drive shaft 41 beforehand through a number ofintermediate pieces and driving units; the end of the shaft 41 may bebevelled to make its insertion easier. The shaft 41 accurately fits inthe square hole in each gear wheel 46. In this way the flexible shaft 41can be readily passed through the intermediate pieces and driving units.

A first possibility of varying the characteristics of the mowing machineis to use intermediate pieces 35 of different lengths, measured in thedirection B. It is also possible to use intermediate pieces 35 of equallengths and to vary the distances between the driving units by arrangingfilling pieces at the ends of the intermediate pieces. In this mannerthe distance between the rotary axes 9 of the cutting units 8 can bevaried. This may be determined by the choice of the directions ofrotation of neighboring cutting units 8. Two adjacent cutting elementshaving the same sense of rotation should not have cutter paths whichoverlap to any appreciable extent. If a standard length of the cutter isused, the length of the intermediate piece located between the drivingunits concerned is selected to be larger than in other cases.Alternatively, the length of the intermediate piece may remain the same,but then shorter cutters must be used. When two adjacent driving unitsrotate in opposite directions, the cutters can overlap considerably inaccordance with the desired local mowing effect. When the standardlength of the cutters of the last-mentioned cutting elements is used ashorter intermediate piece 35 may be used between the two driving units,or, if comparatively long cutters are employed, the intermediate piececan be of standard length. Otherwise if larger diameters of some or allcutting elements and larger diameters of the circles described by thecutter tips are desired, longer intermediate pieces 35 have to be usedso that higher cutting speeds of the cutters can be attained. Thencutter holders 54 of larger diameter are used; in their central partsthey have however the same square recesses receiving the square elevatedpart 55. The later possibility thus provides a second variation inassembling the mowing machine.

It is also possible to select the direction of rotation of each cuttingunit 8. As stated above with reference to FIG. 6 the gear wheel 46together with its integral sleeve 64 can be taken out of the drivingunit 36 by removing the locating ring 61, the Seeger ring (circlip) 62and the bearing 60. FIG. 6 shows the gear wheel on the left-hand side ofthe housing of the driving unit; this disposition determines thedirection of rotation. When the removed parts 46 and 64 are insertedfrom the right-hand side of the housing so that the gear wheel 46engages the right-hand side of the gear wheel 47, the cutting unitmounted on the driving unit will be driven in the opposite direction ofrotation. For this purpose the end of the sleeve 64 away from the gearwheel 46 is moved to the right-hand side of the housing of the drivingunit and the shoulder-like part is caused to bear on the inner race ofthe bearing 60 on the left-hand side. Then on the right-hand side thebearing 60 is inserted, to abut the shoulder near the cavity 75. Finallythe Seeger ring (circlip) 62 is inserted at the right-hand side and thelocating ring 61 is fitted so as to locate the intermediate piece on theright-hand side. These operations are simple to carry out not only bythe manufacturer of the machine but even by a dealer or the userhimself. Of couse driving units having existing dispositions of gearwheel 46 relative to gear wheel 47 can be threaded in a different orderof succession onto the tie rod 42.

The mowing machine described can thus be modified to vary not only thedistance between the rotary axes of the cutting units but also thediameters of the circles described by the tips of the cutters and therelative directions of rotation of adjacent cutting units. Whenassembling the mowing machine in the manner described above attentionshould, of course, be paid to the relative directions of rotation of thecutters, as viewed on plan. The cutters of two adjacent cutting unitswill in general, be disposed so that they are out of phase by a rightangle with respect to one another. It is important for the numbers ofteeth of the gear wheels 46 and 47 of each driving unit to have a givenratio. The ratio between the numbers of teeth of the gear wheels 47 and46 need not be an integer, but should preferably be slightly higher orlower than an integer. In the embodiment described the gear wheel 47 hasthirty-three teeth and the gear wheel 46 has sixteen teeth. When adriving unit is slipped from the right-hand end onto the drive shaft 41(so fixing the square elevated part 55 with respect to the length of theshaft 41) and subsequently an intermediate piece 35 is mounted on theshaft, the shaft 48 of the next driving unit can be turned by handbefore it is slipped onto the shaft 41 until the square part 55 and thesquare recess in the gear wheel 46 have the same positions as those ofthe driving unit already mounted. Owing to the aforesaid ratio betweenthe numbers of teeth of the gear wheels 46 and 47 a few turns of theshaft 48 will be sufficient to cause both the square elevation 55 andthe square recess in the gear wheel 46 to be in the same positions asthose of the driving unit already mounted. Afterwards the cutter holder54 is fitted on the square part 55 in a manner such that the associatedcutters are out of phase by a right angle with respect to those of thedriving unit slipped on previously.

Apart from the aforesaid advantages of the integral drive shaft 41, sucha construction is preferred over an assembly of shaft portions for otherreasons. For example, the individual portions of a composite shaft wouldhave to be coupled together by coupling pieces (for example with asplined connection between the shaft portions and the coupling pieces)so that during operation due to the varying torsional moment in theshaft the shaft portions tend to "bite" the coupling pieces.

Preferably the drive shaft 41 is subjected to a surface treatment toavoid corrosion of the shaft surface; otherwise the passage of thesquare recesses in the gear wheels 46 of the driving units over theshaft might become difficult. Such a surface treatment may be cadmium-or chromium-plating or the like.

As viewed from the side (FIG. 8) the top face of each intermediate piece35 slopes upwardly from front to rear (see the dashed line 77representing the front portion of the top face and the solid line 78representing the rear portion; the solid line located above the dashedline 77 represents an integrally cast ear of the casting near the twoends of the intermediate piece 35, as is also shown, for example, inFIG. 4). Crop passing across the top face of the intermediate piece tothe rear, when the intermediate piece is located, for example, betweentwo cutting units 8 rotating in opposite directions, is guided by theupward slope of the rear part 78 in upwardly and rearwardly inclineddirection as a result of which the crop is airily deposited on theground.

FIG. 9 schematically shows a number of cutting units 8, which have beenassembled in the manner described above to give a desired sequence ofthe various relative distances between the neighboring rotary axes 9 andfor the directions of rotation of the cutting units. The three cuttingunits on the left-hand side of FIG. 9 all rotate in the same sense i.e.clockwise, while the three cutting units on the right-hand side of themachine all rotate in the opposite direction; i.e. counterclockwise.

The mown crop is conveyed from the two ends of the row of cutting unitstowards the center of the machine and is deposited to the rear over andacross the respective intermediate piece 35 in the form of a swath bytwo central cutting units which rotate in opposite directions. In thisembodiment all the mown crop is passed between only two cutting units sothat it is useful in this case for the intermediate piece arrangedbetween the two cutting units driven in opposite senses to be relativelylong compared with the other intermediate pieces 35, or for auxiliarypieces to be provided. The embodiment shown in FIG. 9 is only given byway of example, and the relative dispositions may be different. Forexample, on the left-hand side there could be two cutting units rotatingclockwise, the other four cutting units rotating counterclockwise, butmany other combinations of directions of rotation and relative distancesare also possible. In the embodiment shown in FIGS. 1 and 9 the mowingmachine comprises six cutting units 8 each having a mowing circle thirtycentimeters diameter, when rotating in the same direction, andthirty-five centimeters diameter when rotating in opposite directions,the distance between the rotary axes 9 being about thirty centimetersand the overall cutting width being 1.8 meters. The length of the maindrive shaft 41 is in this case about 165 centimeters. For two adjacentdriving units 36 rotating in the same direction, the distance betweenthe gear wheels 46 is then, of course, also thirty centimeters. For twodriving units driven in opposite directions, the distance between theassociated gear wheels 46 is about thirty-eight centimeters, since thegear wheel 46 of one of the two driving units (see FIG. 6) is put at theright-hand side of the driving unit in its mirror-image position. Thismeans that torsional deformation of the shaft length between the gearwheels 46 of the driving units driven in opposite senses is greater andhence there is more resilience than between the units driven in the samesense so that jolting loads occurring particularly in driving unitsdriven in opposite directions (as in the middle of FIG. 9) can be betterabsorbed.

The FIGS. 10-14 show other embodiments of the cutting units 8 providedon the shafts 48. In the embodiment of the FIGS. 10 and 11 a cuttingholder 86 being provided on the square raised part 55 whereby the squareraised part 55 lies with close fit in a square hole in the cuttercarrier 82 made from strip material, preferably spring steel. From thearea around the square recess fitting around the raised part 55 thecutter carrier 82 is bent on both sides of the center line 9 in adownwardly and outwardly inclined position and terminates on both sidesin a part 83 of the cutter carrier 82 which is perpendicular to thecenter line 9. Near the two ends of the parts 83 of the cutter carrier82 holes are provided for passing fastening parts 84 of the mowingcutters 10 so that the two cutters 10 are located below the ends of thecutter carrier 82. Viewed on plan (broken lines in FIG. 10) each cuttercarrier 82 is outwardly tapering away from its inner part, while the twocutter fastening areas are located diametrically opposite one another.

Above the cutter carrier 82 is located a disc-shaped hood 85. Viewedfrom above (FIG. 10) each hood 85 has, at least in this embodiment, asubstantially circular shape. The upper and inner part 86 of the hood 85is directly bearing on the top and inner part of the cutter carrier 82located around the square raised part 55. At its circular outer edge thepart 86 terminates in a frustoconical part 87, a portion of which is incontact with the top and outer side of the downwardly bent-over part ofthe cutter carrier 82. The top of the cone is located above the cuttingunit and on the center line 9, while its axis coincides with said centreline. The conical part 87 is prolonged to the plane coinciding with thetop side of the part 82 of the cutter carrier 82 and is upwardlyinclined, viewed in the outward direction, away from the latter partlocated at a distance from the outer edge, at an angle of about 10° to20° and far as higher than the fastening parts 84, outside of whichinclination it is downwardly directed to below the nut of the fasteningparts 84 so as to be coupled with the cutter carrier as seen in FIG. 10and 11. The hood 85 terminates near or slightly beyond and at the sideof the imaginary circle going through the outer boundary of the knifecarrier 82.

The hood 85 may be constructed in the form of a rotation-symmetricalbody, but as an alternative it may have the upward inclination shown inFIG. 11 and described in the foregoing exclusively at the place of thecutter connection 84 and, in addition, a similar vault in the area of apart of the periphery which is turned through 90° with respect to thevaulting near the cutter connection, whereas the hood portions lyingbetween said four vaults are perpendicular to the center line 9. Theupward vaults located between the cutter connections are designated inFIGS. 10 and 11 by reference numeral 88.

The inner part of the cutter carrier 84 and the directly superjacentinner part 86 of the hood 85 are both clamped to the subjacent bearingof the cutting unit by means of a locking piece 89 having innerscrewthread and being screwed onto the screwthreaded top end 56 of therotary shaft 48.

In this embodiment the hood 85 may be made from a thin metal sheet, forexample, steel, more particularly spring steel of a thickness of about0.5 to 1.5 millimeters.

The disposition of the cutting carriers 82 and the associated hoods 85of two neighboring cutting units is such that the cutting carriers (and,of course, also the associated hoods 85) are out of phase by an angle of90° with respect to one another. From FIG. 10 it will be apparent that acutter 10 of one of the two cutting units of a pair rotating in oppositesenses passes below the vault 88 of the hood 85 of the other cuttingunit of said pair. If the hoods 85 have a rational-symmetricalstructure, as stated above, a cutter 10 of one cutting unit moves belowthe hood 85 of the other cutting unit during part of its path. The pathscovered by the outermost ends of the cutters 10 of a pair of cuttingunits rotating in opposite senses overlap one another. The distancebetween the cutting connections 84 of the cutting units is in thisembodiment about twenty-five to fifty centimeters, preferably aboutthirty centimeters. In this embodiment the diameter of the pathdescribed by the outermost ends of the cutters is forty to seventy-fivecentimeters, preferably about 50 cms.

The cutters 10 have a slightly torsioned structure in this embodimentsuch that, viewed in the direction of rotation c, the cutting edge ofeach cutter 10 is at a lower level than the rear side of the cutter sothat the cut crop is thrown upwards by the cutter. The crop thus arriveson the rotating hoods 85 of the cutting units. The rapidly rotatinghoods carry the crop across their surfaces into the region between thecenter lines of a pair of oppositely rotating cutting members andfarther in rearward direction. The cutters 10 are freely pivotable aboutpivotal axes substantially parallel to the rotary shafts 9 and formed bythe fastening parts 84. The fastening parts 84, are moreover,constructed so that during operation each cutter 10 can slightly move upand down.

If hard objects such as stones are found on the field to be mown, theseobjects are passed frequently over the main frame 6 (FIG. 11), mainly inthe region where the cutters 10 of a pair of oppositely rotating cuttingunits rotate to the rear. Therefore, these objects have to wriggle inbetween the top side of the main frame 6 and the underside of the hoods85. When the hoods 85 have a flexible structure, they are capable ofbulging upwardly and to allow the object to pass, after which the hoodcan regain its initial shape without damage to the machine. In theembodiment shown in FIGS. 10 and 11 this possibility is in particularoffered by the region below a hood 85 not covered by the associatedcutter carrier 82.

Since the hood 85 is clamped tight only near the inner and upper partsby the locking piece 89 and since the sheet material is thin, greatelasticity of the hood in an upward direction is obtained.

It is noted here that the outermost parts of the hood extending beyondthe frustoconical part 87 are slightly curved upwards in outwarddirection. Owing to the high speed of rotation of the cutting units thecentrifugal forces acting on this part of the hood 85 are relativelyheavy and tend to turn this part of the hood downwards. This effectprovides, so to say, an additional stiffness of the hood so that thehood may have a relatively thin structure and can resist comparativelylarge deformations without being permanently deformed.

The embodiment shown in FIGS. 12, 13 and 14 having the same design ofdrive, frame and cutting carrier as in FIG. 10 and 11 (said parts aredesignated by the same reference numerals) comprises a differentstructure of the hood, which is designated here by reference numeral 90.

The hood 90 has an inner part 91 in the form of a truncated cone beingin engagement with the downwardly extending part of the cutter carrier82. This part 91 terminates near the top side of said downwardlyextending part of the cutter carrier 82. At a distance above the innerregion of the part 83 of the cutter carrier the part 91 goes over into adownwardly inclined part 92 (viewed in section at an angle of about 5°to 20° to a plane perpendicular to the center line 9), which extendsover and beyond the cutter fastening part 84 and beyond the outerboundary of the cutter carrier 83, where it terminates in a downwardlybent-over rim 93 which, as viewed in the sectional view of FIG. 13 is atan angle of about 40° to 70° to a plane perpendicular to the center line9. The lower boundary of the rim 93 is located with some amount ofclearance above the highest boundary of the cutters 10.

The hood 90 has a rotation-symmetrical structure and has a sectionalarea as shown in FIG. 13.

The hood 90 may be made from wear-resistant synthetic resin orrubber-like material provided on its top side with a wear-resistantlayer. In the material of the hood 90 is preferably arranged areinforcement in the form of a plurality of endless reinforcing bars orwires 94 concentric with the center line 9 while near the lower boundaryof the rim 93 a relatively rigid, strong reinforcement 95 is provided insaid rim also in the form of an endless member coaxial with the centerline 9. The reinforcement 95 like the reinforcing bars or wires 94 mayconsist of steel wire and/or a material such as fiber glass. Althoughthis is not indicated in the drawings the hood 90 having the form of aninverted dish without bottom may be provided with reinforcing bars orwires radially directed as viewed in a direction parallel to the centerline 9 and covering the whole radial dimension.

For securing the hood 90 to the downwardly extending inner part of thecutter carrier 82 a plurality of rectangular openings 96 are provided insaid downwardly extending part, whereas near the upper boundary of theconical part 91 of the hood 90 inwardly extending bulging parts 97 areprovided, which are located in the openings 96 of the cutting carrier 82when the hood 90 is mounted. The hood 90 can be put in place without theneed for tools by pressing the part 91 from above to the downwardlyextending part of the cutting carrier, while the material near andbetween the bulging parts initially yields slightly until these bulgingparts snap into the openings 96 so that the hood 90 is fixed withrespect to the cutting carrier. The hood 90 can be disengaged by liftingthe hood near the outer rim and/or by turning it so that such adeformation of the part 91 can be obtained that the bulging parts 97snap out of the openings 96.

As stated above, heavy centrifugal forces occur during operation. Thesecentrifugal forces tend to move upwards the downwardly inclined parts 92and 93 of the hood 90. This is prevented to a considerable extent by thepresence of the reinforcing bar 95, which is exposed to tensile stress,which prevents a further upward deformation. In this way it is ensuredthat despite comparatively slack material sufficient rigidity isobtained for the crop conveying fuction of the hood 90. If a hard objectpasses below the hood 90 and above the frame 6, the flexibility of thehood is, however, sufficient to cause the hood to deform so that theobject can pass by without being jammed and without causing damage. Thehood will locally deform in upward direction, whereas the opposite partof the hood will move slightly downwards. If the passing object isrelatively large and if the flexibility of the hood appears to beinsufficient, the nature of the fixation of the hood with the aid of thebulging parts 97 and the openings 96 (quick-action joint) isadvantageous in that the whole hood is lifted from the cutter carrierand is disengaged from the machine. This does not give rise to danger tothe surroundings because the hood is made of very light-weight materialand will not be slung away as a whole in a given direction likedisengaging cutters. Moreover a screen is fastened to the framework 13.As a matter of course, the hood 90 may be rigidly secured to the innerpart of the cutter carrier by means of bolts or screws.

The two embodiments of the hood are not unrelated. In the embodiment inthin metal as shown in FIGS. 10 and 11 the design of the embodiment ofFIGS. 12, 13 and 14 can be used and for the synthetic resin or rubberstructure of FIGS. 12 and 13 the design of FIGS. 10 and 11 may be used.Moreover, the fastening modes in these two embodiments may beinterchanged. It is furthermore noted that in the two embodiments thehood 85 and 90 respectively need not be rotation-symmetrical; it may beelliptical or substantially elliptical as is shown in FIG. 12 by brokenlines (reference numeral 98).

If the general construction of the mowing machine permits, flexiblehoods having as the case may be, only a screening function may bearranged below the cutter carrier 82 and the cutting fixation.

With regard to the embodiments of the hood 90 it is furthermore notedthat the hoods may be coupled with the cutter carrier by the connectionmembers 84, which contributes to the rigidity of the part of theflexible hood lying beyond said regions in a vertical sense. Moreoverthe embodiment described of the flexible hoods are independent of thenumber of cutters per cutting units and also of the kind of cuttingeffect of the cutter; for example, the flexible hood may also be usedabove or below a cutter or a cutting edge co-operating with a rotatableor non-rotatable counter-knife. Finally, if the construction of themachine permits, the flexible hood may be arranged in a non-rotatablemanner.

The construction of the cutting units with the flexible hood 85 or 90 isvery useful in combination with the construction of the main frame 6 andthe drive shaft 41. The construction of the flexible hoods may, however,also be applied to mowing machines in which the driving gear is locatedabove the cutting units, for example, drum mowers and also to machinesin which the driving members are located both below and above thecutting units. The invention may furthermore be applied to mowingmachines of a different kind of agricultural machines such as combinesand pick-up wagons equipped with cutting units.

The mowing machine described is particularly suitable for being hitchednot only to the rear lift of a tractor but also to a front lift, inwhich case the gear box 26 need only be arranged in a mirror-imageposition with respect to a plane at right angles to the plane of thedrawing in FIG. 4 (particularly the collar 30). A required change ofdirection of rotation of the cutting elements can be carried out in themanner described above. The mowing machine is particularly intended tomow agricultural crop, for example, grass and clover.

Although various features of the mowing machine, described and that areillustrated in the drawings, will be set forth in the following claimsas inventive features, the invention is not necessarily limited to thesefeatures and may encompasses all inventive novel features that have beendisclosed both individually and in various combinations.

Having disclosed our invention which we claim as new and to be securedby Letters Patent of the United States is:
 1. A mowing machine having anelongated main frame comprising a plurality of driving units withcutters along the length thereof, said cutters being rotatable aboutrespective upwardly extending axes and driving means connected to rotatesaid cutters about said axes, said units having end faces which extendacross a major part of their length in the usual direction of operation,a tie member securing said units in place and said tie member extendingthrough aligned apertures of said driving units intermediate the leadingand trailing edges of said frame and approximately midway of each saidend face's length, said tie member being heavily loaded in tension toapply compressive force substantially centrally to said driving units ina direction transverse to the machine's usual direction of operationsand form a rigid main frame that resists bending and is uniformallyloaded.
 2. A mowing machine as claimed in claim 1, wherein the mainframe further comprises a plurality of intermediate pieces at least oneintermediate piece being located between each two adjacent drivingunits, said tie member passing through the intermediate pieces andneighboring driving units, and means for applying tension to said tiemember whereby the intermediate pieces are pressed against the adjacentsaid driving units by the tie member to form the main frame.
 3. A mowingmachine as claimed in claim 2, wherein internal locating rings areprovided between said driving units and said intermediate pieces forpositioning them correctly relative to each other.
 4. A mowing machineas claimed in claim 2, wherein said tie member is positioned aboutmidway between the leading and traiing edges of said main frame.
 5. Amowing machine as claimed in claim 4, wherein only a single cutter unitis mounted on each said driving unit.
 6. A mowing machine as claimed inclaim 4, wherein a main drive shaft extends through all of said drivingunits and each said driving unit includes a gear wheel transmission fortransmitting drive between said drive shaft and respective cutter unitsof said driving units.
 7. A mowing machine as claimed in claim 6,wherein internal locating rings surround said main drive shaft and arepositioned at the junctures of said driving units with said pieces.
 8. Amowing machine as claimed in claim 7, wherein said tie member is locatedbehind said main drive shaft with respect to the normal direction ofoperative travel of the machine.
 9. A mowing machine as claimed in claim8, wherein each said intermediate piece has a front wall located closelyadjacent said main drive shaft.
 10. A mowing machine as claimed in claim6, wherein each said driving unit houses a gear wheel with anon-circular opening that receives said main drive shaft, said gearwheel included in said driving unit's gear wheel transmission, said maindrive shaft having a substantially transverse cross-sectioncorresponding to the shape of said opening in each said gear wheelcontinuously along substantially its entire length.
 11. A mowing machineas claimed in claim 10, wherein said gear wheel can be housed in itscorresponding said driving unit to receive said main drive shaft ineither of two opposite positions so that said cutters can be driven torotate in either direction.
 12. A mowing machine as claimed in claim 6,wherein said gear wheel transmission is so constructed and arrangedthat, in operation, the speed of the rotation of said main drive shaftis substantially higher than the speed of rotation of said cutters. 13.A mowing machine as claimed in claim 6, wherein said tie member extendsthroughout the length of said main frame and is secured to the oppositelateral ends of said main frame.
 14. A mowing machine as claimed inclaim 6, wherein the machine comprises two groups of driving units, eachunit of one said group being located side by side with a unit of theother said group, said cutters of one said group of units being drivento rotate in one direction and said cutters of the other said groupbeing driven to rotate in the opposite direction.
 15. A mowing machineas claimed in claim 2, wherein said main frame is locally supported byshoes that hook on one wall around a rim of each said driving unit, eachshoe being bolted on its other side to the opposite wall of a respectivesaid driving unit, said shoes providing a wear-resistant surface forsaid driving units and supporting the bottom face of each adjacent saidintermediate piece above the ground.
 16. A mowing machine as claimed inclaim 1, wherein a flexible hood which is composed at least in majorpart of a material that is sufficiently deformable within its elasticlimits to prevent stones and like objects from becoming jammedthereunder, is arranged on the upper side of each said driving unit tooverlie said cutters of that said unit.
 17. A mowing machine having anelongated main frame comprising a plurality of driving units withcutters along the length thereof, each driving unit comprising aseparable housing for a gear system connected to a common drive shaftfor said units, at least one intermediate piece disposed between twoadjacent said driving units, a tie rod securing said driving units toclamp said intermediate piece securely in compression between them toform at least part of said main frame, said tie rod being heavily loadedin tension and passing centrally through said driving units and saidintermediate piece so that the mating surfaces of said driving units andsaid intermediate piece are uniformly loaded against each other in adirection transverse to the machines usual direction of travel, saidcommon drive shaft extending through said driving units and saidintermediate piece to operate said driving units via said gear system.18. A mowing machine according to claim 17, wherein said cutters aremounted above said driving units and rotate about substantially verticalaxes.
 19. A mowing machine comprising an elongated main frame having aplurality of separable cutter driving units alternating with separablealternating intermediate pieces along said frame's length, a tie rodsecuring said driving units and said intermediate pieces together toform said main frame, said tie rod received substantially centrallythrough said driving units and through said intermediate pieces betweentheir forward and rearward aspects and being in substantially heavytension to apply compressive forces substantially centrally to saiddriving units and such intermediate pieces so that the entire matingsurfaces of said intermediate pieces and said driving pieces areuniformly loaded, cutters mounted in said driving units and a continuousdrive shaft received through said driving units and said intermediatepieces, said drive shaft being operably interconnected to said cutters.20. A mowing machine according to claim 19 comprising drive gears ineach said driving unit which interconnect said drive shaft and saidcutters in the corresponding said driving unit.